The C.sub.2 hydrocarbons such as acetylene and ethylene are important primary feedstocks in the petrochemical industry and are frequently produced by cracking higher hydrocarbons.
Methane, thermodynamically the most stable hydrocarbon, is the most abundant component of natural gas, usually comprising over 90 mole percent of the hydrocarbon fraction of the gas. Methane is, of course, an important hydrocarbon fuel but it is highly desirable that it be available as a feedstock for manufacture of higher hydrocarbons such as acetylene and ethylene.
Traditionally acetylene has been prepared in a two step process from calcium oxide and carbon, which firstly produces calcium carbide. ##STR1## and then hydrolysis of the calcium carbide to produce acetylene EQU CaC.sub.2 +2H.sub.2 O .fwdarw.C.sub.2 H.sub.2 +Ca(OH).sub.2
This process is, however, highly endothermic as is the high temperature decomposition of methane, with or without a limited quantity of oxygen. ##STR2##
In U.S. Pat. No. 4,574,038, dated 4 Mar. 1986, to Wan, a process to convert methane to ethylene using microwave energy is described. In this process the methane is contacted with a powdered metal catalyst and subjected to a pulse train of microwave radiation.
Microwave energy is also employed in the process described in U.S. Pat. No. 4,975,164, dated 4 Dec. 1990 to Rayella et al, who converted C.sub.2 +hydrocarbons (i.e. C.sub.2 -C.sub.4 saturated hydrocarbons) to primarily unsaturated hydrocarbons and hydrogen, in the presence of one or more plasma initiators. The plasma initiator may be metallic or non-metallic and may include a carbon initiator. It will be noted however, that the carbon initiator is not a reactant as there is already a surfeit of carbon for the reaction. In contrast when water or methane is converted to a C.sub.2 or higher hydrocarbon there is a net deficiency of carbon which must be made up from another source of carbon, such as activated charcoal which is both a catalyst and a co-reactant.